Tapping saddles and also pipe tapping fittings are known from the prior art and are used to connect a branch line to a main pipe. EP 0 679 831 A2 discloses a shaped connecting part for producing branch connections, wherein the heating element used therein has a winding carrier in which the resistance wire is placed in the grooves provided in the winding carrier, and the winding carrier is then embedded in the material of the shaped connecting part.
This embodiment has the disadvantage that a cold zone due to the absence of the resistance wire is formed at the transition to the saddle piece inside diameter in the region of the inside diameter of the pipe stub and this cold zone counts as a weak point in the case of long-term pressure conditions since the pressure of the medium exerts a force on the saddle which leads to the saddle peeling off from the pipe.
In order to provide a remedy, there are versions which reduce the cold zone as far as possible and thereby bring the welding zone closer to the inside diameter of the stub, but this entails the disadvantage that these versions tend to the unwanted emergence of wire and molten material.
EP 0 565 397 A1 discloses a method for producing a heating resistor for welding plastic parts. The heating resistors are produced as grids or, alternatively, as grids in the form of a cylindrical pipe section and are then converted by compressing the cylindrical shape into a flattened collar shape. The disadvantage here is that the heating resistor is not fixed on a support material and therefore the wire undergoes an unwanted relative displacement and wire tends to emerge from the plastic part.
CN 105299372A and JP 5832248 likewise disclose heating windings for tapping saddles which have a special winding pattern. However, the disadvantage with these is that they have a large cold zone in the central region and, as already mentioned, this forms a weak point and the joint readily comes apart there.